Microstructure and tribological performance of ceramic-based self-lubricating sealing coating on a composite substrate

This work used high velocity oxygen fuel spraying technology to prepare three types of ceramic-based self-lubricating sealing coating on C/SiC substrates, with Yttria-stabilized zirconia as the matrix and different mass fractions of Mo and Ag as lubricating phases. The compositions are S1(50%YSZ40%CaF₂10%Mo), S2(50%YSZ40%CaF₂10%Ag) and S3 (40%YSZ30%CaF₂10%Mo10%Ag10%SiO₂). The friction coefficient and wear rate of the coating were examined at room temperature (RT), 400°C and 800°C. The effects of different lubricating phases on the tribological properties of the coating were compared. The wear mechanism of the coating under different temperature environments will be revealed by clarifying the evolution law of the microstructure of the coating. The results show that the addition of Ag can improve the lubricating ability of the coating. Ag element forms a continuous and smooth tribo-layer on the sliding surface to reduce the friction coefficient of the coating. In addition, the lubricating effect of Ag element is more significant at medium and low temperatures. At 800°C, the S3 coating with both Ag and Mo exhibited excellent tribological properties. The wear mechanism of the coating is that it starts with adhesive wear and gradually transitions to abrasive wear as friction continues. This work provides theoretical support and experimental evidence for the construction of ceramic-based self-lubricating sealing coating with a wide temperature range.